1. Field of the Invention
The present invention relates to a hydraulic system used for tool attachments for construction and demolition equipment, for example, a heavy-duty metal cutting shear, a plate sheer, a concrete crusher, a grapple or other construction and demolition equipment. More particularly, the present invention relates to a regeneration manifold for a hydraulic system.
2. Description of Related Art
For purposes of discussion herein, demolition and construction equipment may also be referred to as scrap handling equipment. The description of demolition equipment and construction equipment herein is not intended to be restrictive of the equipment being referenced. Demolition equipment, such as heavy-duty metal cutting shears, grapples and concrete crushers, are mounted on backhoes powered by hydraulic cylinders for a variety of jobs in the demolition field. This equipment provides for the efficient cutting and handling of scrap. For example, in the dismantling of an industrial building, metal scrap, in the form of various diameter pipes, structural I-beams, channels, angles, sheet metal plates and the like, must be efficiently severed and handled by heavy-duty metal shears. Such shears can also be utilized for reducing automobiles, truck frames, railroad cars and the like. The shears must be able to move and cut the metal scrap pieces regardless of the size or shape of the individual scrap pieces and without any significant damage to the shears. In the demolition of an industrial building, concrete crushing devices such as a concrete pulverizer or concrete crackers, are also used to reduce the structure to manageable components which can be easily handled and removed from the site. Wood shears and plate shears also represent specialized cutting devices useful in particular demolition or debris removal situations depending on the type of scrap. Also, a grapple is often utilized where handling of debris or work pieces is a primary function of the equipment. Historically, all of these pieces of equipment represent distinct tools having significant independent capital cost. Consequently, the demolition industry has tended to develop one type of tool that can be used for as many of these applications as possible.
For illustrative purposes, the following discussion will be directed to metal shears. One type of metal shear is a shear having a fixed blade and a movable blade pivoted thereto. The movable blade is pivoted by a hydraulic cylinder to provide a shearing action between the blades for severing work pieces. Examples of this type of shears can be found in prior U.S. Pat. Nos. 4,403,431; 4,670,983; 4,897,921; 5,926,958; and 5,940,971 which are assigned to the assignee of this application and which are herein incorporated in their entirety by reference.
FIG. 1 illustrates a prior art, multiple tool attachment adapted to demolition or construction equipment such as a backhoe (not shown). The multiple tool attachment is adapted to connect one of a series of tools or tool units to the demolition equipment. The tool attached in FIG. 1 is a metal shear 10. The shear 10 includes a first blade 12 connected to an upper jaw 13 and a second blade 14 connected to a lower jaw 15 wherein the jaws 13, 15 are pivotally connected at a hub or main pin 16 to a universal body 18. The body 18 is referred to as universal because it remains common to a series of tools or tool units in the attachment system. The universal body 18 is comprised of sides 19, a bearing housing 20 and a cylinder housing 21. A rotary coupling 23 is between the bearing housing 20 and the cylinder housing 21. The rotary coupling 23 allows for a rotation of the remaining portions of the universal body 18 relative to the bearing housing 20 and the associated demolition equipment. Essentially, the rotary coupling 23 allows for 360° rotation for angular orientation of the universal body 18 and the associated tool such as shear 10. A motor (not shown) is attached to the bearing housing 20 and geared to the rotary coupling 23 for rotationally positioning the universal body 18.
A first linkage 24 is pivotally connected at a removable pivot pin 26 to the first blade 12 and a second linkage 28 is pivotally connected at a removable pivot pin 30 to the second blade 14. The first linkage 24 and the second linkage 28 are pivotally connected to a slide member 32 at a common pivot pin 34. The slide member 32 is attached to a piston rod on a double-acting hydraulic cylinder 38 (partially obscured). The slide member 32 is movable within a slot 44. The hydraulic cylinder 38 is pivotally attached to the universal body 18 through a trunnion 40. Additional details of this arrangement are described in U.S. patent application Ser. No. 10/089,481 filed on Mar. 28, 2002, which is assigned to the same entity as the present application and which is hereby incorporated by reference.
Pressurized hydraulic fluid must be transferred through the rotary coupling 23 to operate the hydraulic cylinder 38. As illustrated in FIGS. 2 and 2A, a manifold 50 is connected to a hydraulic cylinder 38 wherein the manifold 50 is in fluid communication with the hydraulic cylinder 38 but, furthermore, these two parts are permitted to rotate relative to one another by providing the appropriate fluid channels between the manifold 50 and the hydraulic cylinder 38. This technology is known in the art.
A long-standing problem of hydraulic systems utilizing hydraulic cylinders with double-acting pistons exists when the range of motion of a particular tool is large and the forces imparted by the hydraulic cylinder must also be large. One technique for imparting large forces in a hydraulic system is to provide high-pressure fluid against the working surface of a double-acting piston. However, providing such high-pressure fluid may require an inordinately large hydraulic pump or, in the alternative, a smaller pump that provides sufficient pressure but at a lower flow rate. A large pump not only consumes valuable space but, additionally, may be expensive while a smaller pump, because of the lower flow it provides, takes a longer time to operate the double-acting piston. As an example, with a typical industrial metal shear, the time to extend the double-acting piston of a hydraulic cylinder may be six seconds while the time to retract the double-acting piston may be three seconds. The retraction process is faster because the area in which hydraulic fluid may flow within the retraction chamber is smaller than the area within the extension chamber because the piston rod within the retraction chamber consumes area. As a result, an amount of fluid in the retraction chamber will displace the piston a greater amount than the same amount of fluid in the extension chamber. Typically, the retraction time may be twice as fast as the extension time.
A design is needed which speeds up the extension time of the double-acting piston without sacrificing the force provided by the double-acting piston when necessary.